Computing Hydrogen Tunneling Splittings with Nuclear-Electronic Orbital Multireference Configuration Interaction
Rachel J Stein1, Christopher L Malbon1, Sharon Hammes-Schiffer1
1Department of Chemistry, Princeton University, Princeton, New Jersey 08544, United States.
The Journal of Physical Chemistry Letters
|July 23, 2025
Summary
The nuclear-electronic orbital-multireference configuration interaction (NEO-MRCI) method accurately calculates hydrogen and deuterium tunneling splittings. This quantum mechanical approach is crucial for understanding reaction rates and molecular spectra.
Area of Science:
- Quantum Chemistry
- Chemical Physics
Background:
- Hydrogen tunneling significantly influences chemical reaction rates and molecular spectra.
- Accurate quantum mechanical treatment of transferring hydrogen is essential for understanding this phenomenon.
Purpose of the Study:
- To implement and validate the nuclear-electronic orbital-multireference configuration interaction (NEO-MRCI) method for hydrogen tunneling systems.
- To compute nuclear-electronic wave functions and vibronic energies for hydrogen tunneling.
Main Methods:
- The study employed the NEO-MRCI method, which treats nuclei and electrons quantum mechanically at the same level.
- This method incorporates static correlation for hydrogen tunneling and dynamic correlation for vibronic states.
- Calculations were performed for four hydrogen tunneling systems at fixed geometries.
Main Results:
- The NEO-MRCI method successfully computed nuclear-electronic wave functions and vibronic energies.
- Results from NEO-MRCI were compared to numerically exact grid-based calculations.
- The method demonstrated accuracy in calculating hydrogen and deuterium tunneling splittings at fixed geometries.
Conclusions:
- The NEO-MRCI method provides accurate hydrogen and deuterium tunneling splittings at fixed geometries.
- This work establishes NEO-MRCI as a valuable tool for studying hydrogen tunneling systems.
- The findings contribute to a deeper understanding of quantum mechanical effects in chemical processes.
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